1. Field of the Invention
The present invention relates generally to an apparatus and method for transmitting and receiving data in a broadcasting communication system and, more particularly, to an apparatus and a method for controlling a code rate according to data transmission and reception in a broadcasting communication system.
2. Description of the Related Art
Link performance of a broadcasting communication system may degrade due to noise, fading, and Inter-Symbol Interference (ISI). Thus, in order to realize high-speed digital broadcasting communication systems requiring high data throughput and high reliability, it is essential to develop techniques for overcoming the noise, fading, and ISI. In this regard, research has been conducted on error-correcting code for enhancing the communication reliability by efficiently reducing the information distortion. For example, error-correcting codes include Low Density Parity Check (LDPC) code.
Using the LDPC code, an encoder receives an information word including KLDPC-ary bits or symbols and outputs Kparity-ary codeword bits or codeword symbols. When the information word bits (Ksig) which are input into the encoder are smaller than the information word bits KLDPC, a transmitter shortens KLDPC−Ksig bits, and the encoder receives Ksig bits. When parity bits (Ntx_parity), which are required by the transmitter, are smaller than parity bits Nparity output from the encoder, the transmitter punctures Nparity−Ntx-parity bits.
When the shortened bits increase, the code rate decreases. Thus, Bit Error Rate (BER)/Frame Error Rate (FER) performance of the code can get better than the non-shortened code. Meanwhile, when the punctured bits increase, the code rate increases and thus the BER/FER performance can get worse than the non-punctured code. Accordingly, a method for adaptively selecting the number of the shortened bits and the number of the punctured bits based on the length of the information word is required so that similar performance can be maintained irrespective of the information word length, in order to make the system more stable.